The journalist who hounded Lance Armstrong about doping for 13 years says he feels sorry for the cyclist after watching him finally confess.

David Walsh says his sympathy stems from the fact that he did not feel the Texan's apology was heartfelt and drew the conclusion that he had "serious personality issues."

Armstrong admitted to using performance enhancing drugs throughout the years when he won seven Tour de France titles (1999-2005) in an interview with chat-show host Oprah Winfrey. But Walsh, who is the chief sports writer at the Sunday Times, was not convinced he genuinely felt regret.

"I know this is going to sound preposterous but I felt a little bit of sympathy for Armstrong," Walsh told BBC Radio Five Live's Sportsweek.

"Intellectually he had to be remorseful, but emotionally he couldn't do it. Basically, Armstrong knew what he had to do but he wasn't capable of doing it because obviously he's got serious personality issues.

"Lance needed to look remorseful and repentant and you would see a flicker of a smirk crossing his face, and he didn't mean to do that - it was involuntary."

In response to the Irish journalist's unwillingness to believe Armstrong was a clean rider, Armstrong made personal attacks on Walsh by questioning the quality of his journalism and his motives.

One implied accusation was that Walsh had a vendetta against cycling because his son was knocked off his bike and killed at the age of 12. But rather than a personal apology, Walsh added that what he really craved was another interview.

"I'm not looking for an apology, I don't need one and I don't want one," Walsh said. "But if he does offer it, it will be gratefully accepted.

"I would have lots of questions. I would really want to find out what happened to make him the way he turned out to be."